The invention discloses an RTU dual-machine redundant acquisition system based on a synchronous time window, which is composed of a master station, a clock synchronization device, a communication network, a hardware time synchronization network, redundantly configured dual RTUs, multiple IEDs, RIOs, etc. Ethernet is used between RTU and the master station, and Ethernet or field bus is used between RTU and IED / RIO. For the bottom, RTU collects the data of IED and RIO through Ethernet or field bus, and forwards the commands of the master station; for the top, it communicates with the master station through Ethernet, sends the collected data, and accepts the commands of the master station. Through the hardware time synchronization network, the running time of the RTU is divided into uniform time windows that are synchronized between the two RTUs. Each time window is divided into different time intervals, and each time interval completes different tasks in turn. The work between the two machines is completely synchronized, the operating status is completely consistent, the data exchange is reliable, and it can adapt to different working conditions to achieve better redundancy.